Reflective spatial light modulator, optical observation device, and light irradiation device

ABSTRACT

A reflective spatial light modulator includes an electro-optic crystal having an input surface to which input light is input and a rear surface opposing the input surface, a light input/output unit being disposed on the input surface of the electro-optic crystal and having a first electrode through which the input light is transmitted, a light reflection unit including a substrate including a plurality of second electrodes and being disposed on the rear surface side of the electro-optic crystal, and a drive circuit applying an electric field between the first electrode and the plurality of second electrodes. The light input/output unit includes a first charge injection curbing layer formed on the input surface, and the light reflection unit includes a second charge injection curbing layer formed on the rear surface.

TECHNICAL FIELD

The present disclosure relates to a reflective spatial light modulator,an optical observation device, and a light irradiation device.

BACKGROUND ART

For example, Patent Literature 1 and Patent Literature 2 discloseelectro-optical elements. These electro-optical elements include asubstrate, a KTN (KTa_(1-x)Nb_(x)O₃) layer of a ferroelectric substancelaminated on the substrate, a transparent electrode disposed on a frontsurface of the KTN layer, and a metal electrode disposed on a backsurface of the KTN layer. KTN exhibits four crystal structures dependingon a temperature and is utilized as an electro-optical element when ithas a perovskite-type crystal structure. Such a KTN layer is formed on aseed layer which is formed on a metal electrode.

CITATION LIST Patent Literature

[Patent Literature 1] Japanese Unexamined Patent Publication No.2014-89340

[Patent Literature 2] Japanese Unexamined Patent Publication No.2014-89341

SUMMARY OF INVENTION Technical Problem

Patent Literature 1 and Patent Literature 2 disclose that conductivityis applied to a seed layer by adding a conductive substance to the seedlayer. In this case, a metal electrode and a KTN layer are electricallyconnected to each other. Therefore, an electric field can be applied tothe KTN layer. However, in such a configuration, there is concern thatif charge is injected into the KTN layer from the metal electrode, themodulation accuracy may not become stable due to the behavior ofelectrons inside a KTN crystal. Particularly, if conductivity is appliedto a seed layer when a plurality of metal electrodes of anelectro-optical element are formed in an array shape, there is concernthat electrical signals input to the plurality of metal electrodes maybecome mixed and the modulation accuracy may not become stable.

An object of an embodiment is to provide a reflective spatial lightmodulator, a light irradiation device, and an optical observationdevice, in which mixing of electrical signals input to a plurality ofelectrodes can be curbed and modulation accuracy can become stable.

Solution to Problem

According to an aspect, there is provided a reflective spatial lightmodulator modulating input light and outputting modulated modulationlight. The reflective spatial light modulator includes a perovskite-typeelectro-optic crystal having an input surface to which the input lightis input and a rear surface opposing the input surface, and having arelative dielectric constant of 1,000 or higher; a light input/outputunit being disposed on the input surface of the electro-optic crystaland having a first electrode through which the input light istransmitted; a light reflection unit including a substrate on which aplurality of second electrodes are disposed, being disposed on the rearsurface side of the electro-optic crystal, and reflecting the inputlight toward the light input/output unit; and a drive circuit applyingan electric field between the first electrode and the plurality ofsecond electrodes. The light input/output unit includes a first chargeinjection curbing layer formed on the input surface, and the firstcharge injection curbing layer has a dielectric material in a curedproduct made of a non-conductive adhesive material such that injectionof charge into the electro-optic crystal from the first electrode iscurbed. The light reflection unit includes a second charge injectioncurbing layer formed on the rear surface, and the second chargeinjection curbing layer has a dielectric material in a cured productmade of a non-conductive adhesive material such that injection of chargeinto the electro-optic crystal from the plurality of second electrodesis curbed.

In addition, according to another aspect, there is provided an opticalobservation device including a light source outputting the input light,the reflective spatial light modulator described above, an opticalsystem irradiating a target with modulation light output from thespatial light modulator, and a photodetector detecting light output fromthe target.

In addition, according to still another aspect, there is provided alight irradiation device including a light source outputting the inputlight, the reflective spatial light modulator described above, and anoptical system irradiating a target with modulation light output fromthe spatial light modulator.

According to the reflective spatial light modulator, the lightirradiation device, and the optical observation device described above,input light is transmitted through the light input/output unit and isinput to the input surface of the electro-optic crystal. This inputlight can be reflected by the light reflection unit disposed on the rearsurface of the electro-optic crystal and can be output from the lightinput/output unit. At this time, an electrical signal is input betweenthe first electrode provided in the light input/output unit and theplurality of second electrodes provided on the substrate. Accordingly,an electric field is applied to the electro-optic crystal having a highrelative dielectric constant, and thus the input light can be modulated.In this reflective spatial light modulator, the non-conductive firstcharge injection curbing layer is formed on the input surface of theelectro-optic crystal, and the non-conductive second charge injectioncurbing layer is formed on the rear surface of the electro-opticcrystal. Accordingly, injection of charge into the electro-optic crystalfrom the first charge injection curbing layer and the second chargeinjection curbing layer is curbed. Particularly, since the second chargeinjection curbing layer is formed, an electrical signal input to each ofthe plurality of second electrodes is unlikely to spread, and mixingbetween electrical signals is curbed. Therefore, the modulation accuracycan become stable.

In addition, in the aspect, the light reflection unit further includes aplurality of third electrodes being formed on a surface of the secondcharge injection curbing layer on a side opposite to the rear surfaceand corresponding to the plurality of respective second electrodes, anda plurality of bumps being disposed such that the plurality of secondelectrodes and the plurality of third electrodes corresponding to theplurality of second electrodes are electrically connected to each other.In this configuration, when an electric field is applied to theelectro-optic crystal, an electric field can be individually applied tothe plurality of third electrodes. Therefore, mixing of electricalsignals input to a plurality of electrodes can be curbed, and thus themodulation accuracy can become more stable.

In addition, in the aspect, the substrate includes a pixel region inwhich the plurality of second electrodes are disposed and a surroundingregion surrounding the pixel region. The second charge injection curbinglayer has a first region facing the pixel region and a second regionsurrounding the first region. A content of the dielectric material inthe second region is lower than a content of the dielectric material inthe first region. In this configuration, the second region allows asubstrate to be fixed to the rear surface of the electro-optic crystalwith an adhesive force greater than that of the first region.Accordingly, falling-off of a substrate from the electro-optic crystalis curbed.

In addition, in the aspect, a boundary between the first region and thesecond region coincides with a boundary between the pixel region and thesurrounding region when viewed in an input direction of the input light.In this configuration, the electro-optic crystal and the substrate canbe more firmly bonded to each other.

In addition, in the aspect, a boundary between the first region and thesecond region is positioned on a side outward from an edge of a boundarybetween the pixel region and the surrounding region when viewed in aninput direction of the input light. In this configuration, the firstregion can be reliably disposed between the electro-optic crystal andthe pixel region.

In addition, in the aspect, the light input/output unit may furtherinclude a transparent substrate having a first surface to which theinput light is input and a second surface serving as a surface on a sideopposite to the first surface, and the first electrode may be disposedon the second surface of the transparent substrate. In such a spatiallight modulator, even when the electro-optic crystal is formed to bethin in an optical axis direction, the electro-optic crystal can beprotected by the transparent substrate from an external impact or thelike.

In addition, in the aspect, when the relative dielectric constant of theelectro-optic crystal is ε_(xtl), a thickness of the electro-opticcrystal from the input surface to the rear surface is d_(xtl), a sum ofthicknesses of the first charge injection curbing layer and the secondcharge injection curbing layer is d_(ad), and a ratio V_(xtl)/V_(smax)of V_(xtl) indicating a voltage applied to the electro-optic crystal inorder to perform phase modulation or retardation modulation of inputlight by 2π radians to V_(smax) indicating a maximum voltage of anapplication voltage generated by the drive circuit is R_(s), a relativedielectric constant ε_(ad) of the first charge injection curbing layerand the second charge injection curbing layer including the dielectricmaterial may be indicated by Expression 1. In this case, a voltagesufficient for performing phase modulation or retardation modulation ofinput light by 2π radians can be applied to the electro-optic crystal.

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 1} \rbrack & \; \\{ɛ_{ad} > {( \frac{ɛ_{xtl} \cdot R_{s}}{d_{xtl} \cdot ( {1 - R_{S}} )} ) \cdot d_{ad}}} & (1)\end{matrix}$

In addition, in the aspect, the first electrode may be formed on thewhole surface of the input surface. For example, when a plurality offirst electrodes are provided in a manner corresponding to the pluralityof second electrodes, it is difficult to positionally align the firstelectrodes and the second electrodes with each other. In the foregoingconfiguration, there is no need to positionally align the firstelectrode and the second electrodes with each other.

In addition, in the aspect, the light reflection unit may furtherinclude a plurality of third electrodes disposed on the rear surface ofthe electro-optic crystal in a manner of facing the plurality of secondelectrodes. According to this configuration, the plurality of thirdelectrodes can prevent spreading of an electrical signal transferred asan electric line of force.

In addition, in the aspect, in the light reflection unit, the inputlight may be reflected by the plurality of third electrodes. Moreover,in the aspect, in the light reflection unit, the input light may bereflected by the plurality of second electrodes. According to theseconfigurations, there is no need to separately provide a reflectionlayer or the like on the second electrode side.

In addition, in the aspect, the electro-optic crystal may be aKTa_(1-x)Nb_(x)O₃ (0≤x≤1) crystal, a K_(1-y)Li_(y)Ta_(1-x)Nb_(x)O₃(0<x<1 and 0≤y≤1) crystal, or a PLZT crystal. According to thisconfiguration, an electro-optic crystal having a high relativedielectric constant can be easily realized.

In addition, in the aspect, the reflective spatial light modulator mayfurther include a temperature control element for controlling atemperature of the electro-optic crystal. According to thisconfiguration, modulation accuracy can become more stable by maintaininga uniform temperature in the electro-optic crystal.

Advantageous Effects of Invention

According to the reflective spatial light modulator, the lightirradiation device, and the optical observation device of theembodiment, mixing of electrical signals input to a plurality ofelectrodes can be curbed, and thus the modulation accuracy can becomestable.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing a configuration of an opticalobservation device according to an embodiment.

FIG. 2 is a cross-sectional view showing a spatial light modulator usedin the optical observation device in FIG. 1.

FIG. 3 is a view showing a relationship between crystal axes, atraveling direction of light, and an electric field in retardationmodulation.

FIG. 4 is a view for describing an electrode of the spatial lightmodulator in FIG. 2.

FIG. 5 is a cross-sectional view along V-V in FIG. 2.

FIG. 6 is a cross-sectional view showing a spatial light modulatoraccording to another embodiment.

FIG. 7 is a cross-sectional view along VII-VII in FIG. 6.

FIG. 8 is a cross-sectional view showing a spatial light modulatoraccording to another embodiment.

FIG. 9 is a cross-sectional view showing a spatial light modulatoraccording to another embodiment.

FIG. 10 is a cross-sectional view showing a spatial light modulatoraccording to another embodiment.

FIG. 11 is a block diagram showing a configuration of a lightirradiation device according to the embodiment.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments will be specifically described with referenceto the drawings. For the sake of convenience, there are cases in whichthe same reference signs are applied to elements which are substantiallythe same and description thereof is omitted.

First Embodiment

FIG. 1 is a block diagram showing a configuration of an opticalobservation device according to an embodiment. For example, an opticalobservation device 1A is a fluorescence microscope for capturing animage of an observation target. The optical observation device 1Aacquires an image of a specimen (target) S by irradiating a frontsurface of the specimen S with input light L1 and capturing an image ofdetection light L3 such as fluorescence or reflected light output fromthe specimen S in response to the irradiation.

For example, the specimen S which becomes an observation target is asample such as a cell or an organism including a fluorescent materialsuch as a fluorescent dye or fluorescent protein. In addition, thespecimen S may be a sample such as a semiconductor device or a film. Thespecimen S emits the detection light L3 such as fluorescence, forexample, when irradiation with light (excitation light or illuminationlight) having a predetermined wavelength region is performed. Forexample, the specimen S is accommodated inside a holder havingtransmitting properties with respect to at least the input light L1 andthe detection light L3. For example, this holder is held on a stage.

As shown in FIG. 1, the optical observation device 1A includes a lightsource 10, a collimator lens 11, a polarization element 12, apolarization beam splitter 13, a spatial light modulator 100, a firstoptical system 14, a beam splitter 15, an objective lens 16, a secondoptical system 17, a photodetector 18, and a control unit 19.

The light source 10 outputs the input light L1 including a wavelengthfor exciting the specimen S. For example, the light source 10 emitscoherent light or incoherent light. Examples of a coherent light sourceinclude a laser light source such as a laser diode (LD). Examples of anincoherent light source include a light emitting diode (LED), a superluminescent diode (SLD), and a lamp system light source.

The collimator lens 11 collimates the input light L1 output from thelight source 10 and outputs the collimated input light L1. Thepolarization element 12 allows the input light L1 to be selectivelytransmitted therethrough in accordance with a polarization component.For example, the polarization element 12 allows S-wave light of theinput light L1 to be transmitted therethrough. The polarization beamsplitter 13 reflects the input light L1 transmitted through thepolarization element 12 toward the spatial light modulator 100. Thespatial light modulator 100 is a spatial light modulator performingphase modulation or retardation modulation of the input light L1 outputfrom the light source 10. The spatial light modulator 100 modulates theinput light L1 input through the collimator lens 11 and outputsmodulated modulation light L2 toward the polarization beam splitter 13.At this time, the spatial light modulator 100 outputs the modulationlight L2 by rotating a polarization surface of the input light L1 by 90degrees. For this reason, the modulation light L2 output from thespatial light modulator 100 is transmitted through the polarization beamsplitter 13 and is optically guided to the first optical system 14. Thespatial light modulator 100 in the present embodiment is constituted asa reflective type. The spatial light modulator 100 is electricallyconnected to a controller 21 of the control unit 19 and constitutes aspatial light modulation unit. Driving of the spatial light modulator100 is controlled by the controller 21 of the control unit 19. Detailsof the spatial light modulator 100 will be described below. Using thespatial light modulator 100, 1) a position of an irradiation locationcan be limited, 2) the position of the irradiation location can bemoved, 3) a plurality of irradiation locations can be formed at the sametime, and 4) a phase of irradiation light can be controlled.

The first optical system 14 optically joins the spatial light modulator100 and the objective lens 16 to each other. Accordingly, the modulationlight L2 output from the spatial light modulator 100 is optically guidedto the objective lens 16. For example, the first optical system 14 is alens, which concentrates the modulation light L2 from the spatial lightmodulator 100 at a pupil of the objective lens 16.

The beam splitter 15 is an optical element for separating the modulationlight L2 and the detection light L3 from each other. For example, thebeam splitter 15 allows the modulation light L2 having an excitationwavelength to be transmitted therethrough and reflects the detectionlight L3 having a fluorescent wavelength. In addition, the beam splitter15 may be a polarization beam splitter or may be a dichroic mirror.Depending on optical systems (for example, the first optical system 14and the second optical system 17) in front of and behind the beamsplitter 15 or the kind of an applied microscope, the beam splitter 15may reflect the modulation light L2 and may allow the detection light L3having a fluorescent wavelength to be transmitted therethrough.

The objective lens 16 concentrates the modulation light L2 modulated bythe spatial light modulator 100, irradiates the specimen S with theconcentrated light, and optically guides the detection light L3 emittedfrom the specimen S in response to the irradiation. For example, theobjective lens 16 is configured to be able to be moved along an opticalaxis by a driving element such as a piezo-actuator or a stepping motor.Accordingly, a concentration position of the modulation light L2 and afocal position for detecting the detection light L3 can be adjusted.

The second optical system 17 optically joins the objective lens 16 andthe photodetector 18 to each other. Accordingly, an image of thedetection light L3 optically guided from the objective lens 16 is formedby the photodetector 18. The second optical system 17 has a lens 17 afor forming an image of the detection light L3 from the objective lens16 on a light receiving surface of the photodetector 18.

The photodetector 18 captures an image of the detection light L3 whichis optically guided by the objective lens 16 and of which an image isformed on the light receiving surface. For example, the photodetector 18is an area image sensor such as a CCD image sensor or a CMOS imagesensor.

The control unit 19 includes a computer 20 which includes a controlcircuit such as a processor, an image processing circuit, a memory, andthe like; and the controller 21 which includes a control circuit such asa processor, a memory, and the like and is electrically connected to thespatial light modulator 100 and the computer 20. For example, thecomputer 20 is a personal computer, a smart device, a microcomputer, acloud server, or the like. The computer 20 controls operation of theobjective lens 16, the photodetector 18, and the like and executesvarious kinds of control using the processor. In addition, thecontroller 21 controls a phase modulation quantity or a retardationmodulation quantity in the spatial light modulator 100.

Next, the spatial light modulator 100 will be described in detail. FIG.2 is a cross-sectional view showing a spatial light modulator. Thespatial light modulator 100 is a reflective spatial light modulatormodulating the input light L1 and outputting the modulated modulationlight L2. As shown in FIG. 2, the spatial light modulator 100 includesan electro-optic crystal 101, a light input/output unit 102, a lightreflection unit 107, and a drive circuit 110. In the present embodiment,the thickness of the electro-optic crystal 101 in an optical axisdirection may be 50 μm or smaller, for example.

The electro-optic crystal 101 exhibits a plate shape having an inputsurface 101 a to which the input light L1 is input, and a rear surface101 b opposing the input surface 101 a. The electro-optic crystal 101has a perovskite-type crystal structure and utilizes an electro-opticaleffect such as a Pockels effect or a Kerr effect for changing arefractive index. The electro-optic crystal 101 having a perovskite-typecrystal structure is an isotropic crystal which belongs to a point groupm3m of a cubic crystal system and of which a relative dielectricconstant is 1,000 or higher. For example, the relative dielectricconstant of the electro-optic crystal 101 can have a value within arange of approximately 1,000 to 20,000. Examples of such anelectro-optic crystal 101 include a KTa_(1-x)Nb_(x)O₃ (0≤x≤1) crystal(which will hereinafter be referred to as □ a KTN crystal □), aK_(1-y)Li_(y)Ta_(1-x)Nb_(x))₃ (0≤x≤1 and 0≤y≤1) crystal, and a PLZTcrystal. Specifically, BaTiO₃, K₃Pb₃(Zn₂Nb₇)O₂₇,K(Ta_(0.65)Nb_(0.35))P₃, Pb₃MgNb₂O₉, Pb₃NiNb₂O₉, and the like areincluded. In the spatial light modulator 100 of the present embodiment,a KTN crystal is used as the electro-optic crystal 101. Since a KTNcrystal is in an m3m point group of a cubic crystal system, modulationis performed using a Kerr effect instead of a Pockels effect. For thisreason, phase modulation can be performed by inputting light in a mannerof being parallel or perpendicular to crystal axes of the electro-opticcrystal 101 and applying an electric field in the same direction. Inaddition, retardation modulation can be performed when two arbitrarycrystal axes are rotated about the remaining axis by an angle other than0° and 90°. FIG. 3(a) is a perspective view showing a relationshipbetween the crystal axes, a traveling direction of light, and anelectric field in retardation modulation, and FIG. 3(b) is a plan viewshowing each of the axes. The example in FIG. 3 shows a case in whichthe crystal is rotated by an angle of 45°. When the axes X2 and X3 arerotated by 45° about the axis X1 and new axes X1′, X2′, and X3′ are set,retardation modulation can be performed by inputting light in a mannerof being parallel or perpendicular to these new axes. In FIG. 3, anelectric field is applied in an applying direction 1102 of a crystal1104. A propagation direction 1101 of the input light L1 becomesparallel to the applying direction 1102 of an electric field. In thiscase, Kerr coefficients used for modulation of the input light L1 becomeg11, g12, and g44.

The relative dielectric constant of a KTN crystal is likely to beaffected by the temperature. For example, the relative dielectricconstant becomes approximately 20,000 which is the largest at atemperature in the vicinity of −5° C., and the relative dielectricconstant falls to approximately 5,000 at a temperature near 20° C. whichis a normal temperature. Here, the electro-optic crystal 101 iscontrolled such that it has a temperature in the vicinity of −5° C. by atemperature control element P such as a Peltier element, for example.

The light input/output unit 102 has a first electrode 103, a transparentsubstrate 104, a transparent electrode 105, an adhesive layer 106, andan adhesive layer (first charge injection curbing layer) 119. The firstelectrode 103 is disposed on the input surface 101 a side of theelectro-optic crystal 101. For example, the first electrode 103 is atransparent electrode formed of indium tin oxide (ITO), and the inputlight L1 is transmitted therethrough. In the present embodiment, thefirst electrode 103 is formed on the whole surface on the input surface101 a side. The input light L1 is transmitted through the firstelectrode 103 and is input to the inside of the electro-optic crystal101.

For example, the transparent substrate 104 is formed of a material suchas glass, quartz, or plastic in a flat plate shape. The transparentsubstrate 104 has a first surface 104 a to which the input light L1 isinput, and a second surface 104 b which is a surface on a side oppositeto the first surface 104 a and faces the input surface 101 a of theelectro-optic crystal 101. The transparent electrode 105 is an electrodeformed on the whole surface of the second surface 104 b of thetransparent substrate 104, and the input light L1 is transmittedtherethrough. For example, the transparent electrode 105 can be formedon the second surface 104 b of the transparent substrate 104 byperforming vapor deposition of ITO.

The adhesive layer 106 causes the first electrode 103 formed in theelectro-optic crystal 101 and the transparent electrode 105 formed inthe transparent substrate 104 to adhere to each other. For example, theadhesive layer 106 is formed of an epoxy-based adhesive, and the inputlight L1 is transmitted therethrough. For example, conductive members106 a such as metal spheres are disposed inside the adhesive layer 106.The conductive members 106 a come into contact with both the firstelectrode 103 and the transparent electrode 105 and electrically connectthe first electrode 103 and the transparent electrode 105 to each other.For example, the conductive members 106 a are disposed in four cornersof the adhesive layer 106 in a plan view.

The adhesive layer 119 is disposed between the first electrode 103 andthe input surface 101 a and bonds the first electrode 103 and theelectro-optic crystal 101 to each other. The adhesive layer 119 of thepresent embodiment has a first region 119 a forming the center thereofand a second region 119 b surrounding an outer circumference of thefirst region 119 a. The first region 119 a has fine particles of adielectric material in a cured product made of a non-conductive adhesivematerial and includes no conductive material. The term non-conductive isnot limited to properties of having no conductivity and includes highlyinsulating properties and properties of having high electricalresistivity. That is, the first region 119 a has high insulatingproperties (high electrical resistivity) and ideally has noconductivity.

For example, an adhesive material can be formed using an opticallycolorless and transparent resin such as an epoxy-based adhesive. Forexample, the dielectric material can have a relative dielectric constantof the same degree as that of the electro-optic crystal 101, which iswithin a range of approximately 100 to 30,000. The dielectric materialmay be a powder having a particle size equal to or smaller than thewavelength of the input light L1 and can have a particle size within arange of approximately 50 nm to 3,000 nm, for example. Scattering oflight can be curbed by reducing the particle size of the dielectricmaterial. When scattering of light is taken into consideration, theparticle size of the dielectric material may be 1,000 nm or smaller andmay also be 100 nm or smaller. The dielectric material may be a powderof the electro-optic crystal 101. The proportion of the dielectricmaterial in a mixture of an adhesive material and a dielectric materialmay be approximately 50%. For example, the first region 119 a exhibits arectangular shape in a plan view.

The second region 119 b is constituted of a non-conductive adhesivematerial. That is, differing from the first region 119 a, the secondregion 119 b includes no dielectric material such as a powder of theelectro-optic crystal 101. For example, the adhesive material can beformed using an optically colorless and transparent resin such as anepoxy-based adhesive. The second region 119 b may include a dielectricmaterial as in the first region. In such a case, the proportion of thedielectric material in a mixture of an adhesive material and adielectric material is smaller than the proportion thereof in the firstregion 119 a. For example, the first region 119 a exhibits a rectangularframe shape in a plan view.

The first region 119 a can be formed by coating the input surface 101 aof the electro-optic crystal 101 or the first electrode 103 with amixture of an adhesive material and a dielectric material. In addition,the second region 119 b can be formed by coating the input surface 101 aof the electro-optic crystal 101 or the first electrode 103 with anadhesive material.

The light reflection unit 107 is disposed on the rear surface 101 b sideof the electro-optic crystal 101 and reflects the modulation light L2toward the input/output unit. This light reflection unit 107 includes aCMOS substrate (substrate) 108 and an adhesive layer (second chargeinjection curbing layer) 109. The CMOS substrate 108 is fixed to asubstrate 112 such as an organic substrate including a glass epoxy(epoxy resin having a glass fiber sheet as a core material) substrate,or a ceramic substrate with an adhesive layer 111 therebetween, forexample. The CMOS substrate 108 includes second electrodes 108 a whichare a plurality of pixel electrodes facing the rear surface 101 b of theelectro-optic crystal 101. The second electrodes 108 a can reflect theinput light L1 propagated inside the electro-optic crystal 101 towardthe light input/output unit 102. For example, the second electrodes 108a are formed of a material such as a metal (aluminum or the like). Asshown in FIG. 4, in the light reflection unit 107 in the presentembodiment, the plurality of second electrodes 108 a formed to have arectangular shape in a plan view are disposed in a two-dimensionalarray. A length W1 in a transverse direction and a length W2 in avertical direction of the second electrode 108 a can be formed to be thesame length, for example. Second electrodes 108 a adjacent to each otherare disposed with gaps S1 and S2 therebetween. FIGS. 2 and 4schematically show the spatial light modulator 100. For the sake ofsimplification of description, an example in which the second electrodes108 a are disposed in a 4×4 array is described. The CMOS substrate 108may function as a drive circuit applying an electric field between thefirst electrode 103 and the second electrodes 108 a.

Each of the plurality of second electrodes 108 a is provided with acorresponding driving switch 108 b. An arbitrary voltage can becontrolled for each of the second electrodes 108 a using these switches108 b.

The adhesive layer 109 fixes the CMOS substrate 108 to the rear surface101 b. The adhesive layer 109 of the present embodiment has a firstregion 109 a forming the center thereof and a second region 109 bsurrounding an outer circumference of the first region 109 a. Theconfiguration of the adhesive layer 109 is similar to that of theadhesive layer 119 described above. The first region 109 a has aconfiguration similar to that of the first region 119 a, and the secondregion 109 b has a configuration similar to that of the second region119 b.

The first region 109 a can be formed by coating the rear surface 101 bof the electro-optic crystal 101 or the CMOS substrate 108 with amixture of an adhesive material and a dielectric material. In addition,the second region 109 b can be formed by coating the rear surface 101 bof the electro-optic crystal 101 or the CMOS substrate 108 with anadhesive material.

The drive circuit 110 is electrically connected to the first electrode103 and is connected to the CMOS substrate 108, thereby beingelectrically connected to each of the plurality of second electrodes 108a. In the present embodiment, the transparent substrate 104 on thesecond surface 104 b side is formed to have a larger size in a plan viewthan the input surface 101 a of the electro-optic crystal 101. For thisreason, in a state in which the electro-optic crystal 101 is supportedby the transparent substrate 104, a part of the transparent electrode105 formed in the transparent substrate 104 becomes an exposed portion105 a exposed to the outside. The drive circuit 110 is electricallyconnected to this exposed portion 105 a and the CMOS substrate 108. Thatis, since the drive circuit 110 is electrically connected to the firstelectrode 103 with the transparent electrode 105 and the conductivemembers 106 a therebetween, an electric field can be applied between thefirst electrode 103 and the second electrodes 108 a.

The drive circuit 110 is controlled by the control unit 19. The drivecircuit 110 inputs an electrical signal between the first electrode 103and the second electrodes 108 a. Accordingly, an electric field isapplied to the electro-optic crystal 101 and the adhesive layers 109 and119 disposed between the first electrode 103 and the second electrodes108 a. In this case, a voltage applied by the drive circuit 110 isdistributed to the electro-optic crystal 101 and the adhesive layers 109and 119. Therefore, when a voltage applied to the electro-optic crystal101 is V_(xtl), a voltage applied to the adhesive layers 109 and 119 isV_(ad), the relative dielectric constant of the electro-optic crystal101 is ε_(xtl), the thickness of the electro-optic crystal 101 from theinput surface 101 a to the rear surface 101 b is d_(xtl), the relativedielectric constant of the adhesive layers 109 and 119 is ε_(ad), andthe sum of the thicknesses of the adhesive layers 109 and 119 is d_(ad),a voltage ratio R between a voltage applied between the first electrode103 and the second electrodes 108 a and a voltage applied to theelectro-optic crystal 101 is expressed by the following Expression (2).For the sake of simplification of description, the adhesive layer 109and the adhesive layer 119 are formed of materials having the samerelative dielectric constant.

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 2} \rbrack & \; \\{R = {\frac{V_{xtl}}{V_{xtl} + V_{ad}} = \frac{ɛ_{ad} \cdot d_{xtl}}{( {{ɛ_{xtl} \cdot d_{ad}} + {ɛ_{ad} \cdot d_{xtl}}} )}}} & (2)\end{matrix}$

In this manner, a voltage applied to the electro-optic crystal 101depends on the relative dielectric constant ε_(ad) and the thicknessesd_(ad) of the adhesive layers 109 and 119. For example, the spatiallight modulator 100 in the present embodiment has a modulationperformance of outputting the modulation light L2 obtained by modulatingthe input light L1 by one wavelength. In this case, the relativedielectric constant ε_(ad) of the adhesive layers 109 and 119 isobtained as follows. First, the upper limit for a voltage applied to theCMOS substrate 108 by the drive circuit 110 is determined in order toavoid a breakdown of a CMOS circuit. Here, the maximum voltage of anapplication voltage generated by the drive circuit 110 is referred to asV_(smax). In addition, it is assumed that when V_(xtl) is added to theelectro-optic crystal 101 and V_(ad) is added to the adhesive layers 109and 119 respectively, the modulation light L2 modulated by onewavelength is output. At this time, V_(xtl)<V_(xtl)+V_(ad)≤V_(smax) isestablished. Therefore, when a voltage ratio V_(xtl)/V_(smax) betweenV_(xtl) and V_(smax) is R_(s), there is a need for the voltage ratio Rand the voltage ratio R_(s) to satisfy the relationship of the followingExpression (3). In this case, a voltage sufficient for performing phasemodulation of the input light L1 by 2π radians can be applied to theelectro-optic crystal 101.R_(s)<R  (3)

Further, from Expression (2) and Expression (3), the relative dielectricconstant ε_(ad) and the thicknesses d_(ad) of the adhesive layers 109and 119 satisfy the following Expression (4).

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 3} \rbrack & \; \\{R_{S} < \frac{ɛ_{ad} \cdot d_{xtl}}{( {{ɛ_{xtl} \cdot d_{ad}} + {ɛ_{ad} \cdot d_{xtl}}} )}} & (4)\end{matrix}$

From this Expression (4), the relative dielectric constant of theadhesive layers 109 and 119 is obtained. That is, when Expression (4) istransformed into an expression related to the relative dielectricconstant of the adhesive layers 109 and 119, the following Expression(1) is derived.

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 4} \rbrack & \; \\{ɛ_{ad} > {( \frac{ɛ_{xtl} \cdot R_{S}}{d_{xtl} \cdot ( {1 - R_{S}} )} ) \cdot d_{ad}}} & (1)\end{matrix}$

When the relative dielectric constant of the adhesive layers 109 and 119satisfies Expression (1), an electric field sufficient for performingmodulation of the input light L1 by one wavelength can be applied to theelectro-optic crystal.

In addition, when a parameter in indicated by the following Expression(5) is defined using the relative dielectric constant ε_(ad) of theadhesive layers 109 and 119, the thicknesses d_(ad) of the adhesivelayers 109 and 119, the relative dielectric constant ε_(xtl) of theelectro-optic crystal 101, and the thickness d_(xtl) of theelectro-optic crystal 101, it is preferable that the parameter insatisfy m>0.3. In addition, it is more preferable that the parameter insatisfy m>3.

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 5} \rbrack & \; \\{m = \frac{ɛ_{ad} \cdot d_{xtl}}{2 \cdot ɛ_{xtl} \cdot d_{ad}}} & (5)\end{matrix}$

Subsequently, a relationship between the adhesive layer 109, theadhesive layer 119, and the CMOS substrate 108 will be described. In thepresent embodiment, since the adhesive layer 109 and the adhesive layer119 exhibit configurations similar to each other, the adhesive layer 109will be representatively described here. FIG. 5 is a cross-sectionalview along V-V in FIG. 2. As shown in FIG. 5, the CMOS substrate 108includes a pixel region 108 c and a surrounding region 108 d surroundingthe pixel region 108 c. The pixel region 108 c is a region in which theplurality of second electrodes 108 a (refer to FIGS. 2 and 4) aredisposed and which exhibits a rectangular shape as an example. Thesurrounding region 108 d exhibits a rectangular frame shape. The firstregion 109 a of the adhesive layer 109 faces the pixel region 108 c andexhibits a rectangular shape in a plan view. The second region 109 b ofthe adhesive layer 109 surrounds the first region 109 a and exhibits arectangular frame shape in a plan view. A boundary between the firstregion 109 a and the second region 109 b is positioned on a side outwardfrom an edge of a boundary between the pixel region 108 c and thesurrounding region 108 d in a plan view. That is, when viewed in aninput direction of the input light L1, the first region 109 a exhibits arectangular shape larger than the pixel region 108 c. The second region109 b is disposed between the surrounding region 108 d and the rearsurface 101 b of the electro-optic crystal 101.

According to the spatial light modulator 100 described above, the inputlight L1 is transmitted through the first electrode 103 of the lightinput/output unit 102 and is input to the input surface 101 a of theelectro-optic crystal 101. This input light L1 can be reflected by thelight reflection unit 107 disposed on the rear surface 101 b of theelectro-optic crystal 101 and can be output from the light input/outputunit 102. At this time, an electrical signal is input between the firstelectrode 103 provided in the light input/output unit 102 and theplurality of second electrodes 108 a provided on the CMOS substrate 108.Accordingly, an electric field is applied to the electro-optic crystal101 having a high relative dielectric constant, and thus the input lightL1 can be modulated.

In this reflective spatial light modulator 100, the non-conductiveadhesive layer 119 is formed on the input surface 101 a of theelectro-optic crystal 101, and the non-conductive adhesive layer 119 isformed on the rear surface 101 b of the electro-optic crystal 101.

Accordingly, injection of charge into the electro-optic crystal 101 fromthe adhesive layer 109 and the adhesive layer 119 is curbed.Particularly, since the adhesive layer 109 is formed, an electricalsignal input to each of the plurality of second electrodes 108 a isunlikely to spread, and mixing between electrical signals is curbed.Therefore, the modulation accuracy can become stable.

In the configuration of the present embodiment, the higher the relativedielectric constant of the adhesive layers 109 and 119, the easier it isto apply a voltage to the electro-optic crystal 101. For this reason, itis desirable that the content of the dielectric material in the adhesivelayers 109 and 119 be high. However, if the content of the dielectricmaterial is increased, an adhesive force in the adhesive layerdeteriorates. In the present embodiment, the content of the dielectricmaterials in the second regions 109 b and 119 b are lower than thecontent of the dielectric materials in the first regions 109 a and 119a.

For this reason, the second regions 109 b and 119 b allow the CMOSsubstrate 108 and the first electrode 103 to be fixed to theelectro-optic crystal 101 with an adhesive force greater than that ofthe first regions 109 a and 119 a.

The boundary between the first region 109 a and the second region 109 bis positioned on the side outward from the edge of the boundary betweenthe pixel region 108 c and the surrounding region 108 d when viewed inthe input direction of the input light. The area of the first region 109a in a plan view can be larger than the area of the pixel region 108 c.For this reason, positional alignment between the pixel region 108 c andthe first region 109 a can be easily performed.

The first electrode 103 is formed on the whole surface of the inputsurface 101 a. For example, when a plurality of first electrodes 103 areprovided in a manner corresponding to the plurality of second electrodes108 a, it is difficult to positionally align the first electrodes 103and the second electrodes 108 a with each other. In the foregoingconfiguration, there is no need to positionally align the firstelectrode 103 and the second electrodes 108 a with each other.

In the light reflection unit 107, since the input light L1 is reflectedby the plurality of second electrodes 108 a, there is no need toseparately provide a reflection layer or the like on the secondelectrodes 108 a side.

In addition, since the temperature control element P for controlling thetemperature of the electro-optic crystal 101 is provided, a uniformtemperature can be maintained in the electro-optic crystal 101.Accordingly, modulation accuracy can become more stable. The temperaturecontrol may be performed by the temperature control element P targetingnot only the electro-optic crystal 101 but also the spatial lightmodulator 100 in its entirety including the CMOS substrate 108 and thelike.

In addition, in the spatial light modulator 100, phase modulation orretardation modulation can be performed more favorably by forming theelectro-optic crystal 101 to be thin in the optical axis direction. Whenthe electro-optic crystal 101 is formed to be thin in this manner, thereis concern that the electro-optic crystal 101 may be damaged due to animpact or the like from the outside. In the present embodiment, theinput surface 101 a side of the electro-optic crystal 101 is supportedby the transparent substrate 104, and thus the electro-optic crystal 101is protected from an external impact or the like.

Second Embodiment

Subsequently, a spatial light modulator 200 according to the presentembodiment will be described. Points differing from the first embodimentwill be mainly described. The same reference signs are applied toelements or members which are the same, and detailed description thereofwill be omitted.

FIG. 6 is a cross-sectional view showing the spatial light modulator 200according to the present embodiment. As shown in FIG. 6, the reflectivespatial light modulator 200 includes the electro-optic crystal 101, alight input/output unit 202, a light reflection unit 207, and the drivecircuit 110.

The light input/output unit 202 has the first electrode 103, thetransparent substrate 104, the transparent electrode 105, the adhesivelayer 106, and an adhesive layer (first charge injection curbing layer)219. The adhesive layer 219 is disposed between the first electrode 103and the input surface 101 a and bonds the first electrode 103 and theelectro-optic crystal 101 to each other. The adhesive layer 219 of thepresent embodiment has a first region 219 a forming the center thereofand a second region 219 b surrounding an outer circumference of thefirst region 219 a. The first region 219 a can be formed of a materialhaving a composition similar to that of the first region 119 a. Inaddition, the second region 219 b can be formed of a material having acomposition similar to that of the second region 119 b.

The light reflection unit 207 has the CMOS substrate 108 and an adhesivelayer (second charge injection curbing layer) 209. The adhesive layer209 has a first region 209 a forming the center thereof and a secondregion 209 b surrounding an outer circumference of the first region 209a. The configuration of the adhesive layer 209 is similar to that of theadhesive layer 219 described above. The first region 209 a has aconfiguration similar to that of the first region 219 a, and the secondregion 209 b has a configuration similar to that of the second region219 b.

Subsequently, a relationship between the adhesive layer 209, theadhesive layer 219, and the CMOS substrate 108 will be described. Sincethe adhesive layer 209 and the adhesive layer 219 exhibit configurationssimilar to each other, the adhesive layer 209 will be representativelydescribed here. FIG. 7 is a cross-sectional view along VII-VII in FIG.6. As shown in FIG. 7, the first region 209 a of the adhesive layer 209faces the pixel region 108 c and exhibits a rectangular shape in a planview. The second region 209 b of the adhesive layer 209 surrounds thefirst region 209 a and exhibits a rectangular frame shape in a planview. A boundary between the first region 209 a and the second region209 b coincides with the boundary between the pixel region 108 c and thesurrounding region 108 d in a plan view. That is, as in FIG. 7, whenviewed in the input direction of the input light L1, the first region209 a overlaps the pixel region 108 c. For this reason, in FIG. 7, thehidden line indicating the pixel region 108 c overlaps the boundarybetween the first region 209 a and the second region 209 b, andtherefore it is not depicted. The second region 209 b is disposedbetween the surrounding region 108 d and the rear surface 101 b of theelectro-optic crystal 101.

In the present embodiment, since the area of the second region 109 b ina plan view can be increased, the electro-optic crystal 101 and the CMOSsubstrate 108 can be more firmly bonded to each other. In addition, theelectro-optic crystal 101 and the first electrode 103 can be more firmlybonded to each other.

Third Embodiment

Subsequently, a spatial light modulator 300 according to the presentembodiment will be described. Points differing from the first embodimentwill be mainly described. The same reference signs are applied toelements or members which are the same, and detailed description thereofwill be omitted.

FIG. 8 is a cross-sectional view showing the spatial light modulator 300according to the present embodiment. As shown in FIG. 8, the reflectivespatial light modulator 300 includes the electro-optic crystal 101, thelight input/output unit 102, a light reflection unit 307, and the drivecircuit 110. The CMOS substrate 108 constituting the light reflectionunit 107 is fixed to the substrate 112.

The light reflection unit 307 includes the CMOS substrate 108, theadhesive layer 109, a plurality of third electrodes 308, and a pluralityof bumps 309. The CMOS substrate 108 is fixed to the substrate 112. Theplurality of third electrodes 308 are disposed on the rear surface 101 bside of the electro-optic crystal 101. In the present embodiment,similar to the plurality of second electrodes 108 a, the adhesive layer109 formed on the rear surface 101 b is disposed in a two-dimensionalmanner. In this case, the adhesive layer 109 can be formed of the samematerial as that of the first region 109 a. The third electrodes 308 canreflect the input light L1 propagated inside the electro-optic crystal101 toward the light input/output unit 102. For example, the thirdelectrodes 308 are metal electrodes and can be formed of aluminum or thelike. In the present embodiment, the plurality of third electrodes 308formed to have a rectangular shape in a plan view are disposed in atwo-dimensional manner corresponding to the plurality of secondelectrodes 108 a. The plurality of second electrodes 108 a and theplurality of third electrodes 308 face each other. The third electrodes308 can be formed on a surface of the adhesive layer 109 on a sideopposite to the electro-optic crystal 101 by performing vapor depositionof aluminum or the like using a mask pattern.

The plurality of bumps 309 are formed in the same number as the secondelectrodes 108 a and the third electrodes 308. The plurality of bumps309 electrically connect the plurality of second electrodes 108 a andthe plurality of third electrodes corresponding to these secondelectrodes 108 a to each other in one-to-one correspondence. Forexample, the bumps 309 can be formed of gold (Au), a soldering material,or the like. Between the adhesive layer 109 and the CMOS substrate 108,a space between bumps 309 adjacent to each other and a space betweenthird electrodes 308 adjacent to each other may be a gap, for example,or may be filled with an insulating substance.

In this configuration, when an electric field is applied to theelectro-optic crystal, an electric field can be individually applied toa plurality of third electrodes. In addition, since the adhesive layer109 is disposed in a two-dimensional manner, an influence on adjacentpixels can be reduced. Therefore, mixing of electrical signals input toa plurality of electrodes can be curbed, and thus the modulationaccuracy can become more stable.

Fourth Embodiment

Subsequently, a spatial light modulator 400 according to the presentembodiment will be described. Points differing from the first embodimentwill be mainly described. The same reference signs are applied toelements or members which are the same, and detailed description thereofwill be omitted.

FIG. 9 is a cross-sectional view showing the spatial light modulator 400according to the present embodiment. As shown in FIG. 9, the reflectivespatial light modulator 400 includes the electro-optic crystal 101, alight input/output unit 402, the light reflection unit 107, and thedrive circuit 110. The CMOS substrate 108 constituting the lightreflection unit 107 is fixed to the substrate 112.

The light input/output unit 402 is constituted of the first electrode103 and the adhesive layer 119. That is, the light input/output unit 402does not have the transparent substrate 104, the transparent electrode105, and the adhesive layer 106. In the present embodiment, the drivecircuit 110 is connected to the first electrode 103 and the CMOSsubstrate 108. As an example, the first electrode 103 can be formed byperforming vapor deposition of ITO with respect to the cured adhesivelayer 119 which is bonded to the input surface 101 a of theelectro-optic crystal 101. In this configuration, the adhesive layer 119is disposed not for adhesion between the electro-optic crystal 101 andthe first electrode 103 but to mainly curb injection of charge into theelectro-optic crystal 101 from the first electrode 103. For this reason,the adhesive layer 119 shown in the example includes the first region119 a and the second region 119 b. For example, the second region 119 bmay have a composition similar to the composition of the first region119 a.

Fifth Embodiment

Subsequently, a spatial light modulator 500 according to the presentembodiment will be described. Points differing from the first embodimentwill be mainly described. The same reference signs are applied toelements or members which are the same, and detailed description thereofwill be omitted.

FIG. 10 is a cross-sectional view showing the spatial light modulator500 according to the present embodiment. As shown in FIG. 10, thereflective spatial light modulator 500 includes the electro-opticcrystal 101, the light input/output unit 202, a light reflection unit507, and the drive circuit 110.

The light reflection unit 507 includes the CMOS substrate 108, theadhesive layer 109, and auxiliary electrodes (fourth electrodes) 509.The CMOS substrate 108 is fixed to the substrate 112. A plurality ofauxiliary electrodes 509 are disposed on the rear surface 101 b of theelectro-optic crystal 101. The auxiliary electrodes 509 functions as amirror reflecting the input light L1 propagated inside the electro-opticcrystal 101 toward the light input/output unit 102. For example, theauxiliary electrodes 509 are metal electrodes and can be formed ofaluminum or the like. Similar to the second electrodes 108 a formed onthe CMOS substrate 108, the auxiliary electrodes 509 are disposed in atwo-dimensional manner. That is, the auxiliary electrodes 509 and thesecond electrodes 108 a face each other in one-to-one correspondence.

The plurality of auxiliary electrodes 509 are formed on the rear surface101 b side of the electro-optic crystal 101 in a manner of facing theplurality of second electrodes 108 a. The auxiliary electrodes 509 arepositioned in an electrostatic field formed by the first electrode 103of the electro-optic crystal 101 on the input surface 101 a side and thesecond electrodes 108 a. For this reason, an electrostatic field isgenerated between the first electrode 103 and the auxiliary electrodes509 and between the auxiliary electrodes 509 and the second electrodes108 a due to electrostatic induction. That is, the auxiliary electrodes509 function as electrostatic lenses for preventing spreading of anelectrical signal transferred as an electric line of force. Accordingly,in the adhesive layer 109 and the electro-optic crystal 101, spreadingof an electrical signal (that is, an electric line of force) input fromthe drive circuit 110 can be curbed drastically. Therefore, mixing ofinput electrical signals can be further curbed, and thus the modulationaccuracy can become stable with higher resolution.

Hereinabove, the embodiments have been described in detail withreference to the drawings. However, specific configurations are notlimited to these embodiments.

For example, in the foregoing embodiments, the optical observationdevice 1A including a spatial light modulator has been exemplified, butthe embodiments are not limited thereto. For example, the spatial lightmodulator 100 may be mounted in a light irradiation device 1B. FIG. 11is a block diagram showing a configuration of a light irradiationdevice. The light irradiation device 1B has the light source 10, thecollimator lens 11, the polarization element 12, the polarization beamsplitter 13, the spatial light modulator 100, the first optical system14, and the control unit 19 including the computer 20 and the controller21. In this configuration, the specimen S is irradiated with themodulation light L2 output from the spatial light modulator 100 by thefirst optical system 14. Using the spatial light modulator 100, 1) aposition of an irradiation location can be limited, 2) the position ofthe irradiation location can be moved, 3) a plurality of irradiationlocations can be formed at the same time, and 4) a phase of irradiationlight can be controlled.

In addition, the fifth embodiment has shown a configuration in which theauxiliary electrodes 509 formed of a metal reflect the input light L1,but the embodiments are not limited thereto. For example, the auxiliaryelectrodes 509 may be transparent electrodes or may be formed of atransparent film such as ITO, for example. In this case, the input lightL1 can be transmitted through the auxiliary electrodes and can bereflected by the second electrodes 108 a.

In addition, the configurations of the foregoing embodiments can bediverted to each other unless there is any particular contradiction orproblem. In the adhesive layer 109 and the adhesive layer 119 shown inthe third embodiment to the fifth embodiment, the boundary between thefirst region and the second region is positioned on the side outwardfrom the edge of the boundary between the pixel region 108 c and thesurrounding region 108 d. For example, the adhesive layer 109 and theadhesive layer 119 may have a configuration in which the boundarybetween the first region and the second region coincides with theboundary between the pixel region 108 c and the surrounding region 108d.

In addition, an example in which the first region 109 a is formed on thewhole surface of the first region has been described, but theembodiments are not limited thereto. For example, the first region 109 amay be disposed in a two-dimensional manner corresponding to the secondelectrodes 108 a.

REFERENCE SIGNS LIST

1A Optical observation device

1B Light irradiation device

100 Spatial light modulator (reflective spatial light modulator)

101 Electro-optic crystal

101 a Input surface

101 b Rear surface

102 Light input/output unit

103 First electrode

107 Light reflection portion

108 CMOS substrate (substrate)

108 a Second electrode

109 Adhesive layer

110 Drive circuit

509 Auxiliary electrode (third electrode)

L1 Input light

L2 Modulation light

The invention claimed is:
 1. A reflective spatial light modulatormodulating input light and outputting modulated modulation light, thereflective spatial light modulator comprising: a perovskite-typeelectro-optic crystal having an input surface to which the input lightis input and a rear surface opposing the input surface, and having arelative dielectric constant of 1,000 or higher; a light input/outputunit being disposed on the input surface of the electro-optic crystaland having a first electrode through which the input light istransmitted; a light reflection unit including a substrate on which aplurality of second electrodes are disposed, being disposed on the rearsurface of the electro-optic crystal, and reflecting the input lighttoward the light input/output unit; and a drive circuit applying anelectric field between the first electrode and the plurality of secondelectrodes, wherein the light input/output unit includes a first chargeinjection curbing layer formed on the input surface, and the firstcharge injection curbing layer has a dielectric material in a curedproduct made of a non-conductive adhesive material such that injectionof charge into the electro-optic crystal from the first electrode iscurbed, and wherein the light reflection unit includes a second chargeinjection curbing layer formed on the rear surface, and the secondcharge injection curbing layer has a dielectric material in a curedproduct made of a non-conductive adhesive material such that injectionof charge into the electro-optic crystal from the plurality of secondelectrodes is curbed.
 2. The reflective spatial light modulatoraccording to claim 1, wherein the light reflection unit further includesa plurality of third electrodes being formed on a surface of the secondcharge injection curbing layer on a side opposite to the rear surfaceand corresponding to the plurality of respective second electrodes, anda plurality of bumps being disposed such that the plurality of secondelectrodes and the plurality of third electrodes corresponding to theplurality of second electrodes are electrically connected to each other.3. The reflective spatial light modulator according to claim 1, whereinthe substrate includes a pixel region in which the plurality of secondelectrodes are disposed and a surrounding region surrounding the pixelregion, wherein the second charge injection curbing layer has a firstregion facing the pixel region and a second region surrounding the firstregion, and wherein a content of the dielectric material in the secondregion is lower than a content of the dielectric material in the firstregion.
 4. The reflective spatial light modulator according to claim 3,wherein a boundary between the first region and the second regioncoincides with a boundary between the pixel region and the surroundingregion when viewed in an input direction of the input light.
 5. Thereflective spatial light modulator according to claim 3, wherein aboundary between the first region and the second region is positioned ona side outward from an edge of a boundary between the pixel region andthe surrounding region when viewed in an input direction of the inputlight.
 6. The reflective spatial light modulator according to claim 1,wherein the light input/output unit further includes a transparentsubstrate having a first surface to which the input light is input and asecond surface serving as a surface on a side opposite to the firstsurface, and the first electrode is disposed on the second surface ofthe transparent substrate.
 7. The reflective spatial light modulatoraccording to claim 1, wherein when the relative dielectric constant ofthe electro-optic crystal is ε_(xtl), a thickness of the electro-opticcrystal from the input surface to the rear surface is d_(xtl), a sum ofthicknesses of the first charge injection curbing layer and the secondcharge injection curbing layer is d_(ad), and a ratio V_(xtl)/V_(smax)of V_(xtl) indicating a voltage applied to the electro-optic crystal inorder to output the modulation light obtained by modulating a phase ofinput light by 2π radians to V_(smax) indicating a maximum voltage of anapplication voltage generated by the drive circuit is R_(s), a relativedielectric constant ε_(ad) of the first charge injection curbing layerand the second charge injection curbing layer including the dielectricmaterial is indicated by Expression (1). $\begin{matrix}\lbrack {{Math}.\mspace{14mu} 1} \rbrack & \; \\{ɛ_{ad} > {( \frac{ɛ_{xtl} \cdot R_{S}}{d_{xtl} \cdot ( {1 - R_{S}} )} ) \cdot d_{ad}}} & (1)\end{matrix}$
 8. The reflective spatial light modulator according toclaim 1, wherein the first electrode is formed on the whole surface ofthe input surface.
 9. The reflective spatial light modulator accordingto claim 1, wherein the light reflection unit further includes aplurality of fourth electrodes disposed on the rear surface of theelectro-optic crystal in a manner of facing the plurality of secondelectrodes.
 10. The reflective spatial light modulator according toclaim 9, wherein in the light reflection unit, the input light isreflected by the plurality of fourth electrodes.
 11. The reflectivespatial light modulator according to claim 1, wherein in the lightreflection unit, the input light is reflected by the plurality of secondelectrodes.
 12. The reflective spatial light modulator according toclaim 1, wherein the electro-optic crystal is a KTa_(1-x)Nb_(x)O₃(0≤x≤1, KTN) crystal, a K_(1-y)Li_(y)Ta_(1-x)Nb_(x)O₃ (0≤x≤1 and 0<y<1,KLTN) crystal, or a PLZT crystal.
 13. The reflective spatial lightmodulator according to claim 1, further comprising: a temperaturecontrol element for controlling a temperature of the electro-opticcrystal.
 14. An optical observation device comprising: a light sourceoutputting the input light; the reflective spatial light modulatoraccording to claim 1; an optical system irradiating a target withmodulation light output from the reflective spatial light modulator; anda photodetector detecting light output from the target.
 15. A lightirradiation device comprising: a light source outputting the inputlight; the reflective spatial light modulator according to claim 1; andan optical system irradiating a target with modulation light output fromthe reflective spatial light modulator.